Remove Argo CD feature (#403)

We discussed in #381 that we don't know what this is needed for. Let's
remove and re-add if/when it's needed.

Author: robarnold

.devcontainer/devcontainer.json

@@ -61,10 +61,6 @@
       // renovate: datasource=node-version depName=node
       "version": "22.16.0"
     },
-    "ghcr.io/devcontainers-extra/features/argo-cd:1": {
-      // renovate: datasource=github-releases depName=argoproj/argo-cd
-      "version": "2.14.13"
-    },
     "ghcr.io/devcontainers-extra/features/renovate-cli:2": {
       // renovate: datasource=github-releases depName=renovatebot/renovate
       "version": "40.37.1"